The present invention relates to a new romaine lettuce (Lactuca sativa L.) variety designated M8515. All publications cited in this application are herein incorporated by reference.
There are numerous steps in the development of any novel, desirable plant germplasm. Plant breeding begins with the analysis and definition of problems and weaknesses of the current germplasm, the establishment of program goals, and the definition of specific breeding objectives. The next step is selection of germplasm that possess the traits to meet the program goals. The goal is to combine in a single variety or hybrid an improved combination of desirable traits from the parental germplasm. These important traits may include increased head size and weight, higher seed yield, improved color, resistance to diseases and insects, tolerance to drought and heat, and better agronomic quality.
Practically speaking, all cultivated forms of lettuce belong to the highly polymorphic species Lactuca sativa that is grown for its edible head and leaves. As a crop, lettuce is grown commercially wherever environmental conditions permit the production of an economically viable yield. Lettuce is the world's most popular salad. In the United States, the principal growing regions are California and Arizona which produce approximately 329,700 acres out of a total annual acreage of more than 333,300 acres (USDA 2005). Fresh lettuce is available in the United States year-round although the greatest supply is from May through October. For planting purposes, the lettuce season is typically divided into three categories (i.e., early, mid, and late), with the coastal areas planting from January to August, and the desert regions planting from August to December. Fresh lettuce is consumed nearly exclusively as fresh, raw product and occasionally as a cooked vegetable.
Lactuca sativa is in the Cichoreae tribe of the Asteraceae (Compositae) family. Lettuce is related to chicory, sunflower, aster, dandelion, artichoke, and chrysanthemum. L. sativa is one of about 300 species in the genus Lactuca. There are seven different morphological types of lettuce. The crisphead group includes the iceberg and batavian types. Iceberg lettuce has a large, firm head with a crisp texture and a white or creamy yellow interior. The batavian lettuce predates the iceberg type and has a smaller and less firm head. The butterhead group has a small, soft head with an almost oily texture. The romaine, also known as cos lettuce, has elongated upright leaves forming a loose, loaf-shaped head and the outer leaves are usually dark green. Leaf lettuce comes in many varieties, none of which form a head, and include the green oak leaf variety. Latin lettuce looks like a cross between romaine and butterhead. Stem lettuce has long, narrow leaves and thick, edible stems. Oilseed lettuce is a type grown for its large seeds that are pressed to obtain oil. Latin lettuce, stem lettuce, and oilseed lettuce are seldom seen in the United States.
It is desirable to develop new varieties of romaine lettuce having unique combinations of advantageous botanic characteristics, such as a high leaf count, consistent performance in variable temperatures and resistance to diseases.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification.